Method of sealing and gas filling electric lamps



Jan. 13, 1959 v. A. LEVAND ET AL 2,

METHOD OF SEALING ANb GAS FILLING ELECTRIC LAMPS Filed Ma 29, 1956 2 Sheets-Sheet l U lnven tors:

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United States Patent METHGD 0F SEALING AND GAS FILLING ELECTRIC LAMPS Victor A. Le /and, Lyndhurst, and Emmett H. Wiley,

Cleveland, Ohio, assignors to General Electric Company, a corporation of New York Application May 29, 1956, Serial No. 588,043

4 Claims. (Cl- 316-17) Our invention relates to a method of sealing and gas filling electric lamps or similar devices.

The invention is particularly concerned with double ended electric lamps comprising a tubular envelope of vitreous material having a filament extending longitudinally thereof with lead-in conductors connected to the ends of the filament andextending through respective sealed ends of the envelope. It is an object of our invention to provide a method of manufacturing such lamps without the presence of the usual exhaust tip protruding from the side of the envelope. It is a further object to achieve a tipless construction by a method which eliminates the exhaust operation involved in the conventional practice of first sealing the filament in the envelope and then exhausting the envelope through an exhaust tube protruding therefrom, filling the envelope with gas through said tube, and finally tipping cit the tube.

In accordance with one aspect of our invention we achieve the above objects by employing a gas flushing method wherein the air in'the envelope is displaced by flushing an inert gas therethrough from one end of the envelope, and then fusing and compressing the other end of the envelope about. the adjacent lead wire while main taining the pressure of the gas within the envelope substantially at atmospheric to prevent distortion of the plastic envelope material at the sealed area, and then fusing and compressing the first mentioned end of the envelope around the adjacent lead wire to complete the sealing of the envelope with the entrapped gas contained therein as the final filling gas.

Further features and advantages of our invention will appear from the following detailed description and from the drawings wherein:

Fig. 1 is a somewhat schematic and fragmentary elevation of apparatus which may be employed in practicing the invention, and showing the lamp parts in their initial assembled relationship;

Fig. 2 is a perspective view of a lead wire chuck;

Figs. 3 and 4 are fragmentary'elevations showing steps in the performance of sealing and flushing operation;

Fig. 5 is an elevation of a completed lamp; and

Fig. 6 is a fragmentary elevation illustrating a modifiedo technique.

Referring to Fig. 1 of the drawing; the lamp assembly illustrated therein is a heat lamp or infrared radiator comprising a tubular envelope 1 of quartz into which is threaded a coiled tungsten filament 2 having a lead-in conductor 3 of molybdenum wire attached to each end thereof and a plurality of spaced disks 4 of tantalum se- The disks 4 serve the dual functions of supporting the filament 2 in spaced relation from the walls of the envelope 1 and also as a .getter for absorbing deleterious gases in the finished lamp. The lead wires 3 are each provided with a thin intermediate section 5 for forming a hermetic seal with the envelope. Before the filament assembly is inserted'fully into the envelope 1, the outer end of one of the lead wires 3 is inserted into a center aperture 6 (Fig. 2) in the reduced Patented Jan. 13, 1959 'ice end portion 7 of a lead wire chuck 8 and is clamped there in by a hollow headed set screw 9. The said end 7 of chuck 8 is then inserted into the end of the envelope, and the envelope is clamped in the jaws of a holder member 10 of apparatus which may be generally of the type more fully illustrated in application Serial No. 585,519, filed May 17, 1956, by A. G. Foote and V. A. Levand and assigned to the same assignee as the present invention.

The holder 10 is carried by a shaft or sleeve 11 which is rotatably mounted in a block 12 which is slidably mounted on a pair of posts 13 (only one shown) extending vertically from a bed or table 14. At the time the envelope 1 is inserted into the holder 10, the holder is in a raised position from that shown in Fig. l, and it is then lowered by upward movement of a connecting rod 15 extending through the table 14 and connected to a lever 16 which is pivoted at 17 and is connected to one end of a link 18 which is connected to the block 12. The lowermost position of block 12 and holder 10 is determined by a stop collar 19 on one of the posts 13 The lamp 1 is adjusted in the holder 10 so that the lower end thereof is spaced a slight distance from a chuck member 20 which is supported by engagement of a reduced end portion 21 thereof in an aperture 22 in a lug 23 on the table 14.

Before the envelope 1 is brought to its lower-most position, the end of the lower lead wire 3 is inserted into a center bore 24 in the chuck 20 and is clamped therein by the end 25 of a clamping lever 26 which is pivoted on a pin 27 and is held in a normally closed position by a spring 28. While inserting the lead wire 3 the clamp lever 26 is held open by pressure on a button 29 on the lower end thereof. The insertion of the lead wire into the chuck 20 creates a tension in the coiled filament 2.

The envelope 1 is then flushed with an inert gas, preferably argon in this case, from a source of the compressed gas through a flexible supply conduit 38 which is con- ,nected to a tube 31 extending laterally from the chuck 3 and communicating. with internal passages: 32 which extend longitudinally of the chuck it and terminate in openings 33 at the end thereof. The argon gas escapes from the lower end of the envelope 1.

At about the same time that the flow of argon gas is star-ted, heating of the lower end of the envelope is started by flames from oxyhydrogen burners 34 (Fig. 3). When the end of the envelope has been heated to a plastic condition,.it is compressed and flattened at 35 about the thin portion 5 of the lead wire 3 by a pair of pinch clamp jaws 36 to thereby seal the lower end of the envelope. At the same time that the end of the envelope is sealed, a jet of inert gas, such as nitrogen, is directed through a passage 36' in chuck 20 toward the lead Wire 3 to protect it from oxidizing. a v p The envelope is adequately flushed by a flow of argon gas at a pressure just slightly above atmospheric for a period of some 15 seconds or so before the pinch seal is formed. The argon gas is permitted to keep flowing but it is bypassed through the upper end of the envelope by way of a recess 37 (Fig. 2) in the shoulder portion 38 of the chuck 8. The bypassing of the gas assures that the plastic quartz'at and adjacent the seal 391s not distorted by any substantial pressure differential between the atmosphere at the interior and exterior of the envelope.

The lower lead wire 3 is then released from the chuck 20; the lamp is raised by upward movement of the head assembly "of holder .10 and block 12; the holder it) is rotated degrees to invert the lamp; the chuck 29 is displaced by removing it from its support after loosening set screw 23'; the head assembly iii-12 with the lamp 1 and chuck 8 is lowered, and the lower end of the chuck 8 is inserted in the aperture 22. With the argon'still flowing into the envelope and through the bypass recess 37, the then lower end of the envelope is heated by the burners 34 and compressed by the jaws 37 to form the seal 35' (Fig. 4), thus completing the sealing of the lamp with the entrapped argon gas contained therein as the permanent gas filling. The pressure of the argon, at room temperature, is about 500-600 millimeters, depending upon the temperature of the envelope 1 at the time of sealing.

The cullet portion 38 remaining at the end of the envelope is then removed and the lead wire 3 is released from the chuck 8 by loosening the set screw 9. The cullet may be removed by opening the clamp member and bending the envelope 1' to one side to snap off the cullet at the sharp shoulder 39 after which the cullet may be crushed to provide access to the set screw 9. The sharp shoulder 39, as Well a the rounded shoulder 40 at the other end of the seal, is formed by suitable shaping of the pinch jaws 36. The finished lamp appears as 7 shown in Fig. 5.

As illustrated in Fig. 6 the sealing and flushing operations may be performed Without inverting the lamp, and

with the lamp in a horizontal position. The lamp is suitably supported on pads 41 and is held thereon by a clamp 42. The lead Wire 3 at one end is held by the chuck 20. The other lead wire 3 is held by any suitable means, here illustrated as a clamp member 43 which may be provided with a perforated flanged end 44. The lefthand end of the envelope is connected to a supply conduit 45 of argon gas by a suitable port here illustrated simply.

as a flexible conduit 46.

To unite the lamp parts, a How of argon gas is started from the conduit 45 through tube 46, into the left-hand end of the envelope 1 and out the right-hand end. The right-hand end of the envelope is then fused and compressed to seal it by a suitable set of burners and pinch clamp jaws. The flow of argon gas is maintained and, upon formation of the seal 35, the pressure in the envelope isprevented from rising unduly by a relief valve member 47. The said valve 47 comprises a bottle 48 containing a suitable liquid 49 such as butyl phthalate into' which extends a tube 50 which is connected to the conduit 45. The bottle 48 is vented to the atmosphere through a tube 51 so that the pressure in the lamp is limited to a very few millimeters above atmospheric depending upon the height of the liquid 49 above the lower end of the tube 50.

The left-hand end of the envelope 1 is then heated and compressed to form the second seal 35, and the cullet 33 is then removed by snapping it off or severing it with a grinding wheel.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The method of sealing and gas filling an electric V lamp which comprises threading into an envelope of vitreous material a filament having lead wires secured to the end thereof'with the lead wires at, the respective ends of the envelope, introducing a flow of inert gas into one end of the envelope to flush the air therefrom through the other end of the envelope, heating the said other end of the envelope to a plastic condition and compressing it about a portion of the adjacent lead wire to seal said end While maintaining the gas pressure in the envelope at substantially atmospheric, and then heating the said one end of the envelope to a plastic condition and compressing it about a portion of the adjacent lead wire to seal the envelope with the entrapped gas contained therein as the permanent gas filling.

to the ends thereof with the lead wires at the respective ends of the envelope, introducing a flow of inert gas into one end of the envelope to flush the air therefrom through the other end of the envelope, heating the said other end of the envelope to a plastic condition and compressing it about a portion of the adjacent lead wire to seal said end while maintaining the flow of gas into said one end of the envelope and permitting the gas to bypass to the atmosphere through the same one end, and then heating the said one end of the envelope to a plastic condition and compressing it about a portion of theadjacent lead wire to seal the envelope with the entrapped gas contained therein as the permanent gas filling.-

3. The method of sealing and gas filling an electric lamp which comprises threading into a tubular envelope of vitreous material a filament having first and second lead wires secured to opposite ends thereof and with-the end of the firstlead wire gripped in a chuck member extending into the interior of the adjacent first end of the envelope, holding the second lead wire with its end projecting from the opposite second end of the envelope, introducing a flow of inert gas through the chuck member into the first end of the envelope to flush the air therefrom through the second end of the envelope, heating the second end of the envelope to a plastic condition and compressing it about a portion of the second lead wire to seal said end while maintaining the gas pressure in the envelope at substantially atmospheric, heating to a plastic condition an area of the first end of the envelope surrounding the portion of the first lead wire projecting from said chuck member and compressing it about said portion of the lead wire to seal the envelope with the entrapped gas con tained therein as the permanent gas filling, and then severing the portion of said first end of the envelope extending beyond the adjacent seal and removing the chuck member.

4. The method of sealing and gas filling an electric lamp which comprises threading into a tubular envelope of vitreous material a filament having first and second lead wires secured to opposite ends thereof and with the end of the first lead wire gripped in a chuck member extending into the interior of the adjacent first end of the envelope, holding the second lead wire with its end projecting from the opposite second end of the envelope, introducing a flow of inert gas through the chuck member into the first end of the envelope to flush the air therefrom through the second end of the envelope, heating the second end of the envelope to a plastic condition and compressing it about a portion of the second lead wire to seal said end while maintaining the gas pressure in the envelope at substantially atmospheric by continuing the flow of gas through said chuck member into the envelope and permitting it to bypass through the said first end of the envelope by way of a small passage between the chuck member and the said end of the envelope, heating to a plastic condition an area of the first end of the envelope surrounding the portion ofthe first lead wire projecting from said chuck member and compressing it about said portion of the lead wire to seal the envelope with the entrapped gas contained therein as the permanent gas filling, and then severing the portion of said first end of the envelope extending beyond the adjacent seal and removing the chuck member.

Freeman Feb. 17, 1942 Herzog Dec. 25, 1945 

